Roller sail furling and reefing gear has been in use on sailing vessels for many years. Such gear consists basically of an upper rotary bearing or swivel and a rope drum attached to the deck, the drum also being equipped with a rotary bearing. The sail is fitted with a wire rope sewn into its leading edge or luff. The ends of this luff wire are shackled to the upper rotary bearing and to the top of the rope drum. The furling rope is wound on the drum.
To furl the sail, the rope is pulled off the drum as the sheet of the sail is slacked off, and the sail is rolled up around its rotating luff wire, the wire being rotated through its attachment to the drum. To unfurl the sail, the sheet of the sail is pulled while the rope to the drum is slacked off. As the sail unrolls, the luff wire rotates causing the rope drum to rotate and wind the rope upon it ready for furling the sail again when needed.
The sails equipped in the above-described manner can be used without a stay; that is, no mast stay is necessary as the luff of the sail is not clipped to the stay as with conventional sails. In such instances, however, the luff wire of the sail also acts as a supporting stay for the mast, and the sail cannot be changed if the mast is stressed by heavy weather conditions.
More frequently, the roller furling sail is hoisted behind the stay but unattached to it. This proximity to the stay introduces the danger of twisting of the sail, the sail halyard and rotary bearing around the stay, especially in heavy weather conditions. One attachment currently in use shackles the upper rotary bearing to the stay and does help to prevent rotary motion being transferred to the halyard and twisting it while the sail is being furled or unfurled, but does not prevent rotation of the bearing and attached halyard and sail around the stay, causing twisting and fouling. When the halyard, block, bearing and/or sail get twisted around the stay in heavy weather, it becomes impossible to furl the sail with the rotary gear.
Accordingly, there is a need to provide a device which will prevent transfer of rotary motion to the sail halyard and also prevent rotation of the bearing and its attachments around the stay while furling and unfurling the sail or during heavy weather conditions.